In threedimensional integration of semiconductor devices, semiconductor substrates that are provided with structures of integrated circuits, like conductor tracks and electronic circuit components, are stacked and bonded. The conductors that are arranged on different substrates may be connected by through-substrate vias, which are interconnects leading through a substrate. In the case of a silicon substrate these vias are usually designated as through-silicon vias. The via hole in the substrate may be filled with the electrically conductive material or with electrically conductive material and an additional dielectric material.
WO 2009/013315 A2 describes a through-substrate via comprising an unfilled hole in the semiconductor substrate. A terminal contact area surrounds the recess of the via, and a solder ball is deposited so that it closes the recess. In this way a plurality of solder balls may be provided for electric connection, using only a small area of the substrate surface. The diameter of the recess is specified in the range from 50 μm to 500 μm. The solder ball can have a typical dimension of 300 μm to 400 μm side length or diameter.
WO 2011/056374 A2 describes a coaxial through-silicon via.
US 2010/0171209 A1 describes a chip stack comprising gold-plated through-silicon vias, which are interconnected by solder balls provided with a core of a higher melting point. The core, which is adapted to engage in a recess of the via hole, can be copper, tungsten, molybdenum, an insulator or a plastic material.